The invention relates to a load-shiftable transmission for a utility vehicle, comprising a split group, a main group and a range group.
WO 0039484 discloses a transmission, which can be shifted sequentially and without an interruption in traction force, for a motor vehicle, in particular a passenger motor vehicle, with six forward gears. In order to permit a high degree of variability with regard to shift processes without an interruption in traction force, even in the case of multiple up-shifts or downshifts. It is possible for the same transmission gears in the transmission to be used for different power flows via different shift elements and from different input shafts which are assigned to a dual clutch. For this purpose, a gearwheel of an input constant, which is mounted as a loose wheel on an input shaft, can be selectively coupled, by means of shift elements, which act at both sides of the loose wheel, to each input shaft, such that the loose wheel can be driven by both clutches and both input shafts. The transmission also has two countershafts which are driven in each case by an input constant, with one of the countershafts being a hollow shaft which is arranged coaxially with respect to the other countershaft and which is mounted radially within the other countershaft. It is possible for the drive torque to be transmitted from the countershafts to a drive output shaft via three gearwheel planes which are assigned in each case to forward gears, and via a gearwheel plane which is assigned to a reverse gear with the interposition of further shift elements. The transmission has a direct gear, for which an input shaft can be coupled to the drive output shaft of the transmission without the interposition of meshing gearwheel connections.
A patent application assigned to the assignee of the present application with the Ser. No. 12/075,789 and the title “Load-shiftable group transmission”, which was not published before the priority date of the present application, discloses a transmission for a utility vehicle which has a split group, a main group and a range group and which has 12, 16 or 20 forward gears. Also, to ensure power splitting in individual transmission gears, the input shafts which are connected to the dual clutch drive two countershafts, which are arranged coaxially with respect to one another, in each case via an input constant.
Another application assigned to the assignee of the present application with the Ser. No. 12/008,833 and the title “Automatic powershift transmission”, which was not published before the priority date of the present application, discloses a transmission for a utility vehicle, having a split group, a main group and a range group, with the power paths running via the same countershaft in all forward transmission gears with the exception of a direct gear which may be provided. Up to four sequentially power-shiftable transmission gears are possible in the region of a direct gear. The input constants can be selectively connected in each case to an associated input shaft and clutch of the dual clutch. Multiple up-shifts and multiple downshifts and a transfer of a drive torque from one clutch to another clutch for the same transmission gear are not discussed in said document.
Further transmissions in which input constants are assigned in each case to an individual clutch of a dual clutch and the power path extends via one of two coaxial countershafts depending on the clutch which is engaged are known from DE 4330170 C2, DE 10338355 A1 and U.S. Pat. No. 6,460,425 B1.
DE 10102028 A1 or DE 3546454 C2, represent further prior art with regard to transmissions with dual clutches.
It is the principle object of the present invention to provide a load- or power-shiftable transmission which can be used for a utility vehicle and which is improved with regard to structural expenditure, in particular with regard to the shift elements which are to be used, bearing arrangements and installation space, and the capability of shifting under load while simultaneously permitting multiple up-shifts or multiple downshifts without an interruption in traction force.